A new inverse microwave imaging algorithm is presented which has the ability to obtain quantitative dielectric maps of large biological bodies. By using a priori information, obtained with a first order algorithm, the final image is obtained by solving the direct problem and an ill-conditioned system of equations into an iterative procedure. The algorithm has been successfully tested with real dat...
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The author models the step frequency waveform in which the frequency of successive pulses is increased linearly in discrete steps. It is shown how to simultaneously realise the pulse compression and pulse Doppler processing with this waveform to improve the signal to noise ratio and to discriminate against clutter for detection of moving targets
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A method for reducing the Shupe effect in fibre-optic gyros is described, and verified experimentally. The unbalanced phase shifts in the gyro Sagnac intereferometer that are produced by a traversing temperature gradient are randomised by winding the coil in such a way as to scramble the relative positions of the turns
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The authors introduce several new approximations to the cylindrical wire kernel. These approximations are derived from a recently found exact series solution for the cylindrical wire kernel. It is also demonstrated that the well-known reduced kernel and far-zone approximations may be obtained as special limiting cases of this series
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Optical DPSK signalling is employed in unequally spaced WDM transmission systems using dispersion-shifted fibres to reduce the penalty caused by four-wave mixing. More than 10 dB reduction in power penalty is achieved compared with the use of intensity modulation
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The authors report the design and analysis of a six port-TEM cell. The cell is especially useful for EMI/EMC testing since it maximises the test area with high field uniformity in the transverse section and changes the polarisation of fields easily. The measured electric fields inside the cell agree well with the calculated results
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The optimum gain-equalised configuration for the erbium-doped fibre amplifier (EDFA) using a samarium-doped fibre (SDF) is investigated. The dual-pumping scheme with inter-stage SDF and midway isolator was found to be the optimum scheme for obtaining flattened high spectral gain with variation of &les;±0.7 dB and with a low noise figure of &les;5.6 dB within the 1530-1560 nm range. This amp...
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The authors report a GaAs HBT amplifier which achieves a gain efficiency of 2.14 dB/mW at 17 GHz which is believed to be among the highest reported for a self-biased MMIC in this frequency range. The amplifier's optimum gain bias was determined by finding the maxima of a simple bipolar gain-bias function which involves the graphical solution of a transcendental equation. This design calculation wa...
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A channel power equalising WDM link using twincore EDFAs has been investigated. Non-divergent and self-regulating propagation of four wavelength channels is demonstrated in a 910 km link using 14 twincore EDFAs. The inhomogeneous properties of the gain of this new amplifier type are analysed
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A 10 Gbit/s receiver using a Raman preamplifier with a gain of 40 dB and a noise figure of 4.4 dB exhibits a sensitivity of -36.4 dBm (151 photon/bit). The preamplifier which is counter-directionally pumped exhibits a two-stage topology to minimise double Rayleigh scattering
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The authors derive a pruning method for recursive least square (RLS) based algorithms. In this approach, training (on-line type) and pruning are combined. Simulation results showed that this approach is an effective training and pruning method for neural networks
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For a compromised design of microstrip-slotline transitions with multi-arm stubs, the relation between the number of arms and the bandwidth is necessary. This issue is examined using a modelling technique based on the equivalent circuit of the transition. The technique is used to analyse two broadband (1-10 GHz and 5-50 GHz) transitions with stubs having different number of arms
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An algorithm which can extract precise glottal closure instant (GCI) information directly from speech is described. By utilising the average pitch and the area informations, accurate GCI positions are obtained. The result compared with the manually classified GCI information using EGG signals only shows 0.2 ms average error
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A CMOS arithmetic logic unit is presented with a minimum number of transistors and high speed arithmetic operations. Multiple carry chain adders and a novel 1 bit adder, are used in a carry select adder. The carry chain adder has a high degree of shared gates with a low propagation delay
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A simple method for determining the doped fibre length and the pump power of gain-flattened EDFAs has been proposed on the basis of average inversion of the erbium ions with maximum gain flatness. The difference between the obtained and the desired gains to achieve the output power per channel of -5-+5 dBm while maintaining the maximum gain flatness was <±0.3 dB
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GaAs bulk micromachining combined with MESFET technology has been applied to fabricate a thermoelectric microwave power sensor in a terminating load configuration. Its advantages are technological compatibility with MMIC processes combined with excellent performance: the sensitivity under normal ambient pressure is 2.02 V/W, inherent linearity over a dynamic range of 48 dB and a thermal time const...
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A Mach-Zehnder interferometer has been used for the first time in the detection system of a distributed temperature sensor, based on the Landau-Placzek ratio method. The interferometer separates the back-scattered Rayleigh and Brillouin signals with very low losses. Used together with a novel diode-pumped Q-switched fibre laser source, performance has been improved at a substantial cost saving ove...
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A new method for measuring the transmission loss of building components is presented. The component is mounted in the separating wall between two reverberation chambers. The electromagnetic field is diffuse. Comparisons between measurements and theory for a metallic grid validate the method
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The authors present a simple extension of the standard Bussgang blind equalisation algorithms that significantly improves their convergence properties. The technique uses the inverse channel estimate to filter the regressor signal. The modified algorithms provide quasi-Newton convergence in the vicinity of a local minimum of the chosen cost function with only a modest increase in the overall compu...
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A novel Viterbi algorithm of low complexity without carrier recovery is proposed. The most important modification is that the decision metric for surviving paths is not the cumulated variable but its amplitude. Simulation results of its application to MDPSK and convolutional code show negligible performance loss
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Evanescently coupled, waveguide integrated photodiodes were fabricated on InP. The device design is intended to provide ultrafast photoresponse together with a high responsivity. A 3 dB bandwidth of 45 GHz and 90% internal quantum efficiency is achieved at 1.55 μm wavelength. High-speed operation with linear power response is obtained at power levels as high as 5 mW
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Recently, the authors demonstrated improved breakdown characteristics in 1 μm gate length P+-AlInAs/N-AlInAs/GaInAs JHEMTs utilising a junction to modulate the 2-DEG and regrowth of the ohmic contact regions by MOCVD. The authors present high frequency operation (ft and fmax of 62 and 105 GHz, respectively) of 0.2 μm devices with high current (500 mA/mm) and ...
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Electronics Letters is internationally renowned for its rapid communication of new developments and emerging topics across the broad and interdisciplinary field of modern electronics and electrical engineering.